The present novel concept broadly relates to the art of vehicle suspension systems and, more particularly, to a vehicle suspension system utilizing electronically-variable damping based upon an air spring pressure, and a method of controlling a vehicle suspension using the same.
The present novel concept finds particular application and use in conjunction with suspension systems of wheeled vehicles, and will be described herein with specific reference thereto. However, it is to be appreciated that the present novel concept is also amenable to use in other applications and environments, and that the specific uses shown and described herein are merely exemplary.
It is well known that land vehicles of most types and kinds are outfitted with a suspension system that supports a sprung mass of the vehicle (e.g., a body or chassis) on an unsprung mass of the vehicle (e.g., an axle or wheel-engaging member). Known suspension systems typically include a plurality of spring elements (e.g., coil springs, leaf springs, torsion springs and/or air springs) that are responsive to forces and/or loads acting on the sprung and/or unsprung masses of the vehicle. Additionally, known suspension systems commonly include a plurality of damping members for dissipating energy inputs, such as the forces and/or loads acting on the sprung and/or unsprung masses of the vehicle.
It is well understood, however, that damping members undesirably transmit road and other inputs to the sprung mass of a vehicle, and that the level of damping action of the damping member has a relation to the amount or magnitude of the road input that is transmitted through the damping member to the sprung mass of the vehicle. Typically, the more aggressive the damping action of the damping member, the greater amount of the road or other input that is transmitted to the sprung mass of the vehicle. Thus, a more comfortable ride is often achieved with a lower relative damping rate. However, it is also well understood that vehicle performance is affected by the level of damping action of a suspension system and that better handling and/or performance is normally achieved at higher damping rates. As a result, a vehicle manufacturer would, in many cases, compromise between performance and ride quality to avoid either an undesirable decrease in performance due to the use of too low a damping rate, or an undesirably rough ride due to the use of an overly aggressive damping rate.
In an effort to improve performance and/or ride quality of vehicles, suspension systems and/or components thereof have been developed that are operative to vary the damping rate of the damping members in response to inputs acting on the vehicle. One example of variable-rate dampers that are suitable for use in such a suspension system are air proportional dampers, which are well known and normally include an air spring as the operative spring member of the suspension system. Generally, air proportional dampers include valving that is adjusted to vary the damping rate of the damping members in a manner proportional to the changes in the air pressure of the air springs. That is, the valving is in fluid communication with the air spring so that changes in air spring pressure directly change the valving of the damper and, therefore, directly change the damping rate thereof.
However, air proportional dampers and the use thereof introduce certain problems and/or disadvantages that have resulted in the limited adoption and use thereof, at least in certain applications. One disadvantage is that air proportional dampers include various fluid volumes, fittings and connectors that can result in fluid leakage due to the loss of seal integrity at or along the numerous component interconnections. Another disadvantage is that these additional volumes and components utilize valuable space on the vehicle. This can be particularly problematic on smaller or esthetically oriented vehicles, such as passenger vehicles, pickup trucks and sport utility vehicles, for example, where available space for such components is minimal.
As an alternative to mechanically-variable damping members, electronically controlled dampers have been developed. Such devices are commonly used and can include dampers using magnetorheological damping fluid or electrorheological damping fluid as well as dampers using size-variable orifices that are adjustable using an electric motor. Such devices are commonly employed in suspension systems that utilize active or semi-active damping control in which the damping rate of the damping member is continually adjusted based upon road input conditions. That is, active and semi-active damping control schemes adjust the damping rate of the dampers in real time or near-real time based upon sensor signals corresponding to road and/or driving conditions. Generally, the purpose and goal of active and semi-active damping control schemes is to instantaneously sense and counteract road or other inputs to thereby prevent the inputs from reaching the sprung mass of the vehicle, or at least to substantially reduce the magnitude of the road inputs that reach the sprung mass of the vehicle.
However, to be able to sense a road input (e.g., a wheel impact with a pothole), receive and process the data and/or signals from various sensors related to the road input, and then instantaneously make the corresponding adjustments to the electrically adjustable dampers so that the road input can be counteracted before reaching the sprung mass of the vehicle, normally requires substantial processing power and a sophisticated control scheme. Thus, such systems typically operate on a continuous or nearly continuous basis, and are normally quite complex and expensive. As a result, the systems are less well suited for use on more economically priced vehicle models.
Other systems are also known that adjust the damping rate of one or more damping members. One example of such a system is disclosed in U.S. Pat. No. 5,582,385 ('385), which is directed to a method of controlling motion using an adjustable damper. As can be recognized from the '385 patent, however, such systems are often as equally complex as those used for active or semi-active control systems. For example, the '385 patent utilizes numerous components and control algorithms that are together used to calculate the magnitude of an input force acting on a mass. The system then instantaneously generates a counteracting response using a continuous force-controlled type damper.
Accordingly, it is desirable to develop a vehicle suspension system and method of controlling the same that overcomes the foregoing and other problems and disadvantages.